Recombinant fusion protein formulation

ABSTRACT

Provided is a liquid formulation that enables the stable storage of recombinant fusion proteins, comprising a recombinant fusion protein, a buffer salt, a stabilizer, and a surfactant.

TECHNICAL FIELD

The present invention belongs to the field of biotechnical pharmaceutical formulations, and in particular relates to stable recombinant fusion protein formulations, preparing methods and use thereof.

BACKGROUND ART

Age-related macular degeneration (AMD), also known as senile macular degeneration, is a senescent change of the retinal macular structure, and mainly is irreversible decrease or loss of vision caused by retinal pigment epithelial cells and retinal degeneration. The disease is clinically divided into dry (atrophic) AMD and wet (exudative) AMD, of which, wet AMD accounts for about 20% of the total number of AMD cases. But in western countries, wet AMD is the main reason of blindness for the aged. Intraocular abnormal vascular proliferation is one of the main causes of the occurrence and development of wet AMD, and blocking abnormal vascular proliferation is the basis of treatment of wet AMD. It may slow down or even prevent the disease process. Vascular endothelial growth factor (VEGF) is a secretory protein that can induce angiogenesis, increase vascular permeability, and cause inflammation. And these factors are closely related to the development of wet AMD. Therefore, in the development of medicaments for treating wet AMD, VEGF is a potential therapeutic target.

Recombinant fusion protein of human vascular endothelial growth factor receptor-antibody-human complement receptor 1 (hereinafter referred to as IBI302) is a macromolecule designed and developed for AMD disease based on the above mechanism. It is a new drug of State Category I with global intellectual property designed by the applicant. The route of administration is designed for intravitreal injection, and the dose is expected to be 0.5˜2 mg/eye.

Since 1982, after the introduction of the first recombinant drug (artificial insulin), more and more recombinant fusion protein drugs have been developed by protein engineering technology. Some of them have been accepted as conventional drugs. However, because such drug is a polypeptide or protein with large molecular weight, its performance is very unstable, prone to deterioration, and very likely to self-aggregation under high concentration of the protein. These unfavorable factors make a great challenge to making these drugs into stable, safe and effective formulations.

Recombinant fusion protein is a biomacromolecule, structure of which is very complex. During production and storage process, a variety of physical and chemical changes will occur in the expressed protein molecules. Physical changes are: adsorption, unfolding denaturation, aggregation and precipitation. Chemical changes are: deamidation, isomerization, oxidation and so on. These changes may influence the safety and effectiveness of the final product. Therefore, it is important to establish a suitable formulation to protect the stability and safety of the product.

IBI302 is a double-target specific fusion protein and is a new drug of State Category I. Due to its complex structure, the protein is unstable in chemical properties, and is prone to aggregation and the charge isomers are easily converted from the alkaline component to the acidic component.

Therefore, there is still a need in the art to develop recombinant protein formulation for protecting the stability of the product.

SUMMARY OF INVENTION

One object of the present invention is to provide a recombinant fusion protein formulation, which can stabilize the fusion protein at a higher concentration. In addition, the formulation can maintain its stability under conditions of high temperature acceleration, long term refrigeration and repeated freezing and thawing, thereby improving the clinical use safety.

In the first aspect of the present invention, a liquid formulation of a recombinant fusion protein is provided, which comprises a recombinant fusion protein, a buffer salt, a stabilizer, a surfactant and sterile water for injection, wherein,

the concentration of the recombinant fusion protein is 5 to 45 mg/mL;

the buffer salt is selected from citrate salt, acetate salt or any combination thereof, and the concentration of the salt is 5 to 25 mmol/L, preferably 8-22 mmol/L;

the stabilizer is selected from sodium chloride, an amino acid or a polyol (polyhydric alcohol) or any combination thereof, wherein the amino acid is selected from arginine, glycine, histidine or any combination thereof, and the polyol is selected from sucrose, sorbitol, mannitol or any combination thereof; and the concentration of sodium chloride is 100 to 200 mmol/L; the concentration of amino acid is 50 to 350 mmol/L; and the concentration of polyol is 1-15 wt %, based on total weight of the liquid formulation;

the surfactant is selected from polysorbate 20, polysorbate 80, poloxamer 188, or any combination thereof and the concentration of the surfactant is 0.01-0.08 wt %, based on total weight of the liquid formulation;

and the pH of the liquid formulation is from 4.5 to 7.5.

In another preferred embodiment, the recombinant fusion protein is a recombinant fusion protein of human vascular endothelial growth factor receptor-antibody-human complement receptor 1, amino acid sequence of which is shown in SEQ ID NO. 1 or SEQ ID NO. 3.

In another preferred embodiment, the stabilizer is selected from an amino acid, polyol and any combination thereof.

In another preferred embodiment, the concentration of sodium chloride is 120 to 180 mmol/L.

In another preferred embodiment, the concentration of amino acid is 70 to 260 mmol/L.

In another preferred embodiment, the concentration of polyol is 3-10 wt %. In another preferred embodiment, the concentration of polyol is 200 to 300 mmol/L, preferably of 220 to 270 mmol/L.

In another preferred embodiment, the pH of the liquid formulation is from 5.0 to 7.2, preferably is from 5.5 to 7.0.

In another preferred embodiment, the buffer salt is citrate; the amino acid is arginine; the polyol is sucrose; and the surfactant is polysorbate 20.

In the present invention, the buffer salt is sodium citrate, sodium acetate or a combination thereof.

In the second aspect of the present invention, a kit is provided which comprises a liquid formulation according to the first aspect of the present invention and a container containing the liquid formulation.

Further, the kit further contains an instruction.

In the third aspect of the present invention, a use of the liquid formulation according to the first aspect of the present invention for preparing a medicament for prevention and/or treatment of age-related macular degeneration is provided.

In another preferred embodiment, the age-related macular degeneration is wet age-related macular degeneration.

The liquid formulation of the present invention can keep the recombinant fusion protein stable, so that the recombinant protein can be stably present in the prescription drugs, the quality of the product can be improved, the shelf life is prolonged and the safety of clinical use is improved. The liquid formulation has good thermal stability, and can remain stable in the high temperature acceleration, long-term refrigeration and repeated freezing and thawing conditions.

It should be understood that in the present invention, the technical features specifically described above and below (such as the examples) can be combined with each other, thereby constituting a new or preferred technical solution, which needs not be specified one by one.

DETAILED DESCRIPTION OF INVENTION

Through extensive and intensive researches, the inventors have unexpectedly and firstly discovered a recombinant fusion protein formulation which can keep the product stable under the acceleration, long-term and freeze-thaw conditions. Recombinant fusion proteins (VEGF inhibitors) that can be used in the present invention also include recombinant fusion proteins (VEGF inhibitors) obtained by other genetic engineering techniques. Based on this discovery, the inventors have completed the present invention.

Recombinant Fusion Protein of Human Vascular Endothelial Growth Factor Receptor-Antibody-Human Complement Receptor 1

The preferred recombinant recombinant protein of the present invention is a recombinant fusion protein of human vascular endothelial growth factor receptor-antibody-human complement receptor 1 (see U.S. 61/629,932(PCT/US2012/067489); title of invention: Protein inhibitors to complement and VEGF pathways and Methods of use thereof); the amino acid sequence of which is shown in SEQ ID NO. 1.

Another preferred recombinant fusion protein of the present invention is a recombinant fusion protein of human vascular endothelial growth factor receptor-antibody-human complement receptor 1, the amino acid sequence of which is shown in SEQ ID NO. 3.

Liquid Formulation

The liquid formulation of a recombinant fusion protein of the present invention comprises a recombinant fusion protein, a buffer salt, a stabilizer, a surfactant and sterile water for injection.

In another preferred embodiment, the liquid formulation comprises a recombinant fusion protein, a buffer salt, sodium chloride, a surfactant and sterile water for injection.

In another preferred embodiment, the liquid formulation comprises a recombinant fusion protein, a buffer salt, a polyol, a surfactant and sterile water for injection.

In another preferred embodiment, the liquid formulation comprises a recombinant fusion protein, a buffer salt, an amino acid, a surfactant and sterile water for injection.

In another preferred embodiment, the liquid formulation comprises a recombinant fusion protein, a buffer salt, a polyol, an amino acid, a surfactant and sterile water for injection.

The concentration of recombinant fusion protein is 5 to 45 mg/Ml.

The buffer salt is one or a combination of two or more kinds of citrate salt, and acetate salt, and the concentration of the salt is 5 to 25 mmol/L, preferably of 8-22 mmol/L.

The stabilizer is one or a combination of two or more kinds of sodium chloride, an amino acid and a polyol.

The amino acid is one or a combination of two or more kinds of arginine, glycine, and histidine. The concentration of amino acid is 50 to 350 mmol/L, preferably of 70-260 mmol/L.

The polyol is one or a combination of two or more kinds of sucrose, sorbitol, and mannitol. The concentration of polyol is 1-15 wt %, preferably of 3-10 wt %.

The concentration of sodium chloride is 100-200 mmol/L.

The surfactant is one or a combination of two or more kinds of polysorbate 20, polysorbate 80, poloxamer 188.

The concentration of surfactant is 0.01-0.08 wt %, preferably of 0.02-0.06 wt %, based on total weight of the liquid formulation.

The pH of the liquid formulation is from 4.5 to 7.5, preferably is 5.0-7.0.

The liquid formulation of the present invention or a kit comprising the liquid formulation can be used for the preparation of a medicament for the prevention and/or treatment of age-related macular degeneration. The recombinant protein can be maintained stable, the product can be of high quality and long shelf life and the safety of clinical use is improved.

The features mentioned above, or the features mentioned in the examples, may be combined in any combination. All features disclosed in this specification may be used in conjunction with any form of the composition, and each of the features disclosed in the specification may be substituted by any alternative feature that provides the same, equal or similar purpose. Thus, unless otherwise specified, the features disclosed are only general examples of equal or similar features.

The main advantages of the present invention comprise:

(1) The present invention provides a novel formulation with a longer shelf life that allows the recombinant fusion protein, such as the recombinant fusion protein of human vascular endothelial growth factor receptor-antibody-human complement receptor 1 remain stable. The formulation can remain stable under the high temperature acceleration, long-term refrigeration and repeated freezing and thawing conditions.

(2) In the liquid formulation of the present invention, the physicochemical stability of the recombinant fusion protein formulation can be improves, so that the recombinant protein can be stably present in the prescription drug, the quality of the product is improved, the shelf life is prolonged and the safety of clinical use is improved.

The present invention will be further illustrated below with reference to the specific examples. It should be understood that these examples are only to illustrate the invention, not to limit the scope of the invention. The experimental methods with no specific conditions described in the following examples are generally performed under the conventional conditions (e.g., the conditions described by Sambrook et al., Molecular Cloning-A Laboratory Manual Cold Spring Harbor Laboratory Press, 1989), or according to the manufacture's instructions. Unless indicated otherwise, parts and percentage are calculated by weight.

Unless otherwise defined, all professional and scientific terms used herein have the same meaning as those skilled in the art are familiar with. In addition, any method and material similar to or equivalent to the contents described herein may be applied to the method of the present invention. The preferred embodiments and materials described herein are for exemplary purposes only.

General Method

SEC-HPLC method: is performed according to Appendix III B of “Pharmacopoeia of the People's Republic of China” (2010 edition, part three), hydrophilic silica gel size exclusion column is used in detection, and the purity of the sample is calculated with area normalization method.

Charge isomerization (cIEF): the sample was ionized by applying a voltage at both ends of the capillary by using a Beckman capillary electrophoresis (Model:

PA800 plus) and a coated capillary Neutral Capillary (50 μm i.d×45 cm). After ionization, the plot was integrated and analysised with 32 Karat software, and calculated according to the area normalization method.

DSC: MIcroCal VP-DSC was used, the starting temperature was 10° C., the end temperature was 110° C., and the scanning rate was 60° C./Hr. The final Tm values of each sample were obtained after subtracting the corresponding buffer.

EXAMPLE 1

The Effect of Amino Acids, Polyols and Sodium Chloride on the Stability of Fusion Protein

Various solutions were prepared with sterile injectable water as shown in Table 1, and the fusion protein (amino acid sequence as shown in SEQ ID NO. 3) was subjected to ultrafiltration substitution with the prepared respective solutions.

The ultrafiltration substitution fluid with the fusion protein concentration of 10 mg/ml was diluted to 1.5 mg/ml with the corresponding solution. Then, 1.5 ml of the dilution was taken and an appropriate amount of polysorbate 20 was added to a final concentration of 0.03% by weight. A sample for detection was obtained after filtration using a 0.2 μm filter.

In addition, 5 ml of the solution described in Table 1 was taken and an appropriate amount of polysorbate 20 was added so that the final concentration thereof was 0.03% and then filtered through a 0.2 μm filter as a buffer blank control. The Tm values for different protein stabilizers were measured by DSC method. The experimental results were shown in Table 2.

TABLE 1 Effects of Different Kinds of Protein Stabilizers on the Stability of Fusion Protein Buffer No. components Stabilizer pH Value 1-1 10 mmol/L Sucrose 8% by weight 6.2 1-2 Sodium citrate Sorbitol 250 mmol/L 6.2 1-3 Sodium chloride 150 mmol/L 6.2 1-4 Histidine 150 mmol/L 6.2 1-5 Glycine 250 mmol/L 6.2 1-6 Arginine 150 mmol/L 6.2 1-7 Arginine 80 mmol/L + Sucrose 6.2 5% by weight 2-1 10 mmol/L Sucrose 8% by weight 6.2 2-2 Sodium acetate Sorbitol 250 mmol/L 6.2 2-3 Sodium chloride 150 mmol/L 6.2 2-4 Histidine 150 mmol/L 6.2 2-5 Glycine 250 mmol/L 6.2 2-6 Arginine 150 mmol/L 6.2 2-7 Arginine 80 mmol/L + Sucrose 6.2 5% by weight

2: DSC Results of Different Kinds of Protein Stabilizer No. Tm Value (° C.) 1-1 57.95 1-2 58.16 1-3 58.51 1-4 58.58 1-5 57.64 1-6 58.60 1-7 58.61 2-1 53.27 2-2 53.25 2-3 57.60 2-4 58.59 2-5 52.32 2-6 58.40 2-7 57.33

The final Tm values of the respective samples were obtained by subtracting the corresponding solution blanks from 14 different samples. The results showed that all of 14 samples exhibited high thermal stability. Wherein the thermal stability of sample groups 1-1, 1-2, 1-3, 1-4, 1-5, 1-6, 1-7, 2-3, 2-4, 2-6, 2-7 was the best followed by that of sample groups 2-1, 2-2, 2-5. The results showed that the recombinant fusion protein formulations consisting of components of Table 1 and the recombinant fusion protein exhibited better thermal stability.

EXAMPLE 2

pH Stability

Solutions of each pH were prepared with sterile injectable water according to Table 3, and the fusion protein (amino acid sequence as shown in SEQ ID NO. 3) was subjected to ultrafiltration substitution with the prepared solutions.

The ultrafiltration substitution fluid with the fusion protein concentration of 10 mg/ml was diluted to 1.5 mg/ml with the corresponding solution. Then, 1.5 ml of the dilution was taken and an appropriate amount of polysorbate 20 was added to a final concentration of 0.03% by weight. A sample for detection was obtained after filtration using a 0.2 μm filter.

In addition, 5 ml of the solution of each pH value was taken and an appropriate amount of polysorbate 20 was added so that the final concentration thereof was 0.03% and then filtered through a 0.2 μm filter as a buffer blank control. The Tm values for on different pH value were measured by DSC method. The experimental results were shown in Table 4.

TABLE 3 Samples used in pH Stability Example No. pH Buffer Stabilizer 1 5.5 Sodium citrate 10 Arginine 80 mmol/L + mmol/L Sucrose 5% by weight 2 6.0 Sodium citrate 10 Arginine 80 mmol/L + mmol/L Sucrose 5% by weight 3 6.0 Sodium acetate 10 Arginine 80 mmol/L + mmol/L Sucrose 5% by weight 4 6.5 Sodium acetate 10 Arginine 80 mmol/L + mmol/L Sucrose 5% by weight 5 7.0 Sodium citrate 10 Arginine 80 mmol/L + mmol/L Sucrose 5% by weight 6 7.5 Sodium citrate 10 Arginine 80 mmol/L + mmol/L Sucrose 5% by weight

TABLE 4 DSC results of pH stability No. pH Tm Value (° C.) 1 5.5 59.58 2 6.0 59.89 3 6.0 59.75 4 6.5 59.87 5 7.0 54.85 6 7.5 52.75

The Tm values of the different samples of 6 groups obtained by subtracting the corresponding buffer showed that the samples 1-4 exhibited high thermal stability followed by sample 5, and the Tm of sample 6 was slightly lower, indicating that the recombinant fusion protein exhibited high thermal stability within pH 5.5-7.0.

EXAMPLE 3

Formulation of Recombinant Fusion Protein Human Vascular Endothelial Growth Factor Receptor-Antibody-Human Complement Receptor 1

The formulation was prepared according to the following formula and the amino acid sequence of the fusion protein was shown in SEQ ID NO. 3.

Formulation A

the recombinant fusion protein 10 mg/ml; Sodium citrate 10 mmol/L; Arginine 80 mmol/L; Sucrose 5 wt %; Polysorbate 20 0.03 wt %; pH 6.2 Solvent the sterile water for injection

Under the sterile condition, the semi-finished product was subpackaged into the vials, and stamped with rubber stoppers and aluminum plastic covers to obtain finished products.

Formulation B

The recombinant fusion protein 40 mg/ml; Sodium citrate 10 mmol/L; Arginine 80 mmol/L; Sucrose 5 wt %; Polysorbate 20 0.03 wt %; pH 6.2 Solvent the sterile water for injection

Under the sterile condition, the semi-finished product was subpackaged into the vials, and stamped with rubber stoppers and aluminum plastic covers to obtain finished products.

EXAMPLE 4

Accelerated Stability Experiment

The samples of Example 3 were stored in a 25° C. incubator for accelerated stability experiments. After one month, the samples were taken out and compared with the test results at 0 days to measure the accelerated stability of the formulation under high temperature conditions. The results were shown in Table 5 and Table 6.

TABLE 5 The results of changes in protein charge isomerization at 25° C. ± 2° C. (PI > 8.0) Sample name 0 day 1 month Formulation A (10 mg/ml) 68.75% 68.87% Formulation B (40 mg/ml) 67.82% 68.45%

TABLE 6 The results of changes in protein purity at 25° C. ± 2° C. (percentage of SEC main peak) Sample name 0 day 1 month Formulation A (10 mg/ml) 99.23% 99.01% Formulation B (40 mg/ml) 99.03% 98.51%

The chemical stability of the recombinant fusion protein was characterized by capillary isoelectric focusing (cIEF) and protein purity (SEC-HPLC). The change in the percentage of isoelectric point PI>8.0 and the content of main peak of protein purity (SEC-HPLC) were used as the determination means. The results showed that the charge isomer content in Formulations A and B did not significantly change after 1 month of accelerated experiment (see table 5). At the same time, the main peak content in the Formulations A and B did not significantly change (see Table 6), while other indicators, such as appearance, protein concentration, turbidity and so on in the accelerated conditions did not significantly change. The results showed that, at 25° C., the recombinant fusion protein in both of two formulations could maintain stabile for at least 1 month.

EXAMPLE 5

Long-Term Stability Experiment

The sample used in this example was the same as that of Example 4, i.e., the formulation prepared in Example 3. The samples were stored in a 2-8° C. incubator for long-term stability experiments. The samples were taken out at the third and sixth month and compared with the test results at 0 day to measure the Long-term stability of the formulation at low temperature.

The experimental results were shown in Tables 7 and 8.

TABLE 7 The results of changes in protein charge isomerization at 2-8° C. (PI > 8.0) Sample name 0 day 3 months 6 months Formulation A (10 mg/ml) 56.68% 56.65% 55.20% Formulation B (40 mg/ml) 56.42% 55.90% 55.27%

TABLE 8 The results of changes in protein purity at 2-8° C. (percentage of SEC main peak) Sample name 0 day 3 months 6 months Formulation A (10 mg/ml) 99.23% 99.32% 99.09% Formulation B (40 mg/ml) 99.03% 99.09% 98.64%

The results showed that there was no significant change in charge isomerization (cIEF) and protein purity (SEC-HPLC) within 6 months under long-term storage conditions at 2-8° C. While other indicators, such as appearance, protein concentration, turbidity and so on did not significantly change under the acceleration conditions. The results showed that both of two formulations could be stored for at least 6 months under long term conditions.

EXAMPLE 6

Freeze-Thaw Stability

The sample used in this example was substantially the same as the formulation of Example 3, except that the amino acid sequence of the fusion protein was shown in SEQ ID NO. 1. The samples were frozen at −80° C. and thawed at room temperature. The samples were repeatedly freeze-thawed for three times or six times. The results were shown in Tables 9 and 10.

TABLE 9 The results of changes in protein charge isomerization under freeze-thaw conditions (PI > 8.0) Sample name 0 three times six times Formulation A (10 mg/ml) 65.99% 65.00% 64.99% Formulation B (40 mg/ml) 65.81% 63.55% 63.71%

TABLE 10 The results of changes in protein purity under freeze- thaw conditions (percentage of SEC main peak) Sample name 0 three times six times Formulation A (10 mg/ml) 99.23% 99.31% 99.22% Formulation B (40 mg/ml) 99.03% 98.99% 99.02%

The results showed that there was no significant change in the charge isomerization (cIEF) and protein purity (SEC-HPLC) for the three groups of sample after freeze-thaw 6 times, and other test indicators, such as appearance, and visible foreign matter related to the physical properties were qualified. The results showed that the physical and chemical properties of the formulation were still stable after freezing and thawing at least 6 times.

The results of the above studies showed that the liquid formulation prepared by using the buffer and the stabilizer of the present invention and the recombinant fusion protein exhibited good stability, and the fusion protein can be stably preserved at a higher concentration. The formulation could remain stable under the high temperature acceleration, long-term refrigeration and repeated freezing and thawing conditions, and the safety of clinical use can be improved.

All documents referred to in the present invention are incorporated by reference as if each reference is cited alone as a reference in the present application. In addition, it should be understood that after reading the teachings of the present invention described above, a skilled person in the art can make various changes or modifications of the invention, and these equivalent forms also fall into the scope as defined by the appended claims of the present application. 

1. A liquid formulation of a recombinant fusion protein, which comprises a recombinant fusion protein, a buffer salt, a stabilizer, a surfactant and sterile water for injection, wherein, the recombinant fusion protein has a concentration of 5 to 45 mg/mL; the buffer salt is selected from citrate salt, acetate salt or any combination thereof, and has a concentration of 5 to 25 mmol/L; the stabilizer is selected from sodium chloride, an amino acid or a polyol or any combination thereof, wherein the amino acid is selected from arginine, and the polyol is selected from sucrose, sorbitol, mannitol or any combination thereof; and the sodium chloride has a concentration of 100 to 200 mmol/L; the amino acid has a concentration of 50 to 350 mmol/L; and the polyol has a concentration of 1-15 wt%, based on total weight of the liquid formulation; the surfactant is selected from polysorbate 20, polysorbate 80, poloxamer 188, or any combination thereof and has a concentration of 0.01-0.08 wt%, based on total weight of the liquid formulation; and the pH of the liquid formulation is from 4.5 to 7.5; the recombinant fusion protein is a recombinant fusion protein of human vascular endothelial growth factor receptor-antibody-human complement receptor 1 which has an amino acid sequence as shown in SEQ ID NO. 1 or SEQ ID NO.
 3. 2. The liquid formulation of claim 1, wherein the recombinant fusion protein is a recombinant fusion protein of human vascular endothelial growth factor receptor-antibody-human complement receptor 1 which has an amino acid sequence as shown in SEQ ID NO.
 1. 3. The liquid formulation of claim 1, wherein the stabilizer is selected from an amino acid, polyol and any combination thereof.
 4. The liquid formulation of claim 1, wherein sodium chloride has a concentration of 120 to 180 mmol/L.
 5. The liquid formulation of claim 1, wherein the amino acid has a concentration of 70 to 260 mmol/L.
 6. The liquid formulation of claim 1, wherein the polyol has a concentration of 220 to 270 mmol/L.
 7. The liquid formulation of claim 1, wherein the pH of the liquid formulation is from 5.0 to 7.2.
 8. The liquid formulation of claim 1, wherein the pH of the liquid formulation is from 5.5 to 7, and the liquid formulation comprises: the recombinant fusion protein 5-45 mg/ml; citrate 5-15 mmol/L; arginine 50-100 mmol/L; sucrose 2-8 wt %; polysorbate 20 0.02-0.06 wt %; and the sterile water for injection.


9. The liquid formulation of claim 1, wherein the buffer salt is citrate; the polyol is sucrose; and the surfactant is polysorbate
 20. 10. The liquid formulation of claim 1, wherein the pH of the liquid formulation is from 5.5 to 7.0.
 11. The liquid formulation of claim 1, wherein the buffer salt is selected from citrate, acetate or any combination thereof, and has a concentration of from 8 to 22 mmol/L.
 12. A kit which comprises a liquid formulation according to claim 1 and a container containing the liquid formulation.
 13. A use of a liquid formulation according to claim 1 or a kit for preparation of a medicament for prevention and/or treatment of age-related macular degeneration.
 14. The use of claim 13, wherein the age-related macular degeneration is wet age-related macular degeneration. 